A future in which doctors can deliver medicines through the body with extreme precision is fast approaching. Researchers at ETH Zurich have developed a revolutionary microrobot that can deliver medicines to exactly the right place, for example to dissolve a blood clot in the brain or to treat tumours directly. This innovation marks a major step towards minimally invasive therapies and smart precision medicine.
Every year, around 12 million people worldwide suffer a stroke. For many of them, this results in permanent disability or even death. Current treatments consist of administering drugs to dissolve blood clots. However, these drugs spread throughout the body, requiring a high dose to deliver the right amount of medication to the site of the blockage. This increases the risk of serious side effects, such as internal bleeding.
‘Medications are often only needed in one place in the body,’ explains Dr Fabian Landers, postdoctoral researcher at the Multi-Scale Robotics Lab at ETH Zurich. ‘Our goal was to find a way to deliver medications exactly where they need to do their job.’
The new microrobot makes this possible. The robot can navigate through the body and deliver medication directly to the site of the problem, such as a blood clot, an infection or a tumour. The ETH team published the research results in the leading journal Science.
Magnetically controlled drug delivery robot
The microrobot consists of a spherical capsule made of soluble gel material, measuring only a fraction of a millimetre. Iron oxide nanoparticles are incorporated into this gel, making the robot magnetic. This allows it to be controlled remotely via electromagnetic fields. ‘The blood vessels in the human brain are extremely narrow,’ says Landers. ‘The challenge was to develop a robot that is small enough to move through these vessels, but at the same time has strong enough magnetic properties to remain controllable.’
Visibility is also crucial. To track the robot's location, the researchers added tantalum nanoparticles. These are materials that are often used as contrast agents in X-ray examinations. This allows the team to see in real time how the microrobot moves through the blood vessels.
According to Professor Bradley Nelson, professor of microrobotics at ETH Zurich, combining magnetic control, imaging and precision was a huge technical challenge: ‘We spent years working to find the right balance between materials science and robotics. The robot not only had to be visible, but also remain controllable under the high pressure and speed of the bloodstream.’
Magnetic navigation
To steer the robot accurately through the body, the team developed a modular electromagnetic navigation system suitable for use in operating theatres. The researchers combine three different magnetic strategies that together enable stable control, even in fast-flowing blood.
Depending on the magnetic field, the robot can roll along the vessel wall, move against the blood flow or navigate through branches of the vascular system. This allows it to reach speeds of up to 4 millimetres per second, an impressive achievement on a micro scale. ‘The speed of blood flow varies greatly depending on where you are in the body,’ explains Nelson. ‘Our robot has to be able to withstand those dynamics. That makes control extremely complex.’
Once the robot has reached the right place, a high-frequency magnetic field can be applied. This heats the iron oxide nanoparticles, causing the gel capsule to dissolve and the drugs to be released in a controlled manner. In this way, the active ingredient ends up exactly where it is needed, without damaging surrounding tissues. The video below gives an idea of how it works.
Innovative catheter technology
The microrobots are introduced into the blood or cerebrospinal fluid via a specially designed catheter. The catheter is based on a commercial model with an internal guide wire and a flexible polymer grip. As soon as the microrobot approaches its destination, the grip opens and releases the capsule, which then navigates independently to the target area.
This system proved to be highly effective in laboratory conditions. The researchers tested the technology in silicone models of human and animal blood vessels, which are so realistic that they are now also used for medical training. These models were developed by Swiss Vascular, a spin-off from ETH Zurich. ‘These realistic models allowed us to optimally tune the robot and the navigation strategy,’ says Professor Salvador Pané, co-researcher and chemist at the Institute of Robotics and Intelligent Systems.
Successful animal trials
The laboratory tests were followed by trials on pigs and sheep, in which the researchers demonstrated that all three navigation methods are also effective in living tissue. In more than 95 per cent of cases, the microrobot was able to reach its target location and deliver the drug.
The robot also remained clearly visible throughout the entire journey, which is crucial for safe clinical application. Landers emphasises that the technology is not limited to the treatment of strokes: ‘We also see great potential in the treatment of local infections or tumours. For example, the robot can deliver antibiotics or cancer medication directly to the right place, without affecting the rest of the body.’
Clinical application
The next step for the ETH team is to start clinical trials in humans. The aim is to make the technology suitable for use in hospitals and operating theatres. ‘Doctors are already doing a great job,’ says Landers, ‘but they don't yet have tools that can intervene with such precision at the microscopic level. What motivates us is the knowledge that in the future we will be able to help patients faster and more safely, with fewer side effects.’
According to Professor Nelson, the research is also an example of how robotics, nanotechnology and medical science are coming together to shape the medicine of tomorrow. ‘Magnetic fields are ideal for minimally invasive procedures,’ he explains. ‘They penetrate deep into the body and, at the frequencies we use, have no harmful effects. This technology could fundamentally change the way we treat diseases.’
With this development, ETH Zurich is taking an important step towards a future in which microrobots navigate through the bloodstream as precision instruments of medicine. What once seemed like science fiction may soon become reality: microscopic doctors that, guided by magnetic fields, deliver medicines exactly where they are needed, quickly, safely and effectively.
Magnetic microrobots
Two years ago, an important step was taken in Twente (Netherlands) in the development of magnetic microrobots for surgical applications. Researchers at the Surgical Robotics Laboratory at the University of Twente succeeded in getting two magnetic microrobots to work together. These robots, only 1 millimetre in size, were able to pick up, move and stack objects in a three-dimensional environment.
This achievement marked a breakthrough in biomedical applications, such as operations in hard-to-reach places in the body where traditional surgery is impossible. The microrobots are biocompatible, which means that they can function safely in the human body without causing harmful reactions.
A major challenge was magnetic control: because the robots attract each other, researchers had to develop a special control system to control them accurately and independently. Thanks to this precision, the robots may be able to perform non-invasive procedures in the future, such as targeted drug delivery, stopping bleeding or destroying tumours.
